دانلود رایگان ترجمه مقاله اثر شیب بستر بر رفتار شمع پلاتفرم ثابت دریایی تحت نیروهای جانبی – اسپرینگر 2015

مقاله انگلیسی رایگان

ترجمه فارسی رایگان 

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Abstract

Fixed offshore platforms supported by pile foundations are required to resist lateral load due to wave and current forces. The response to environmental loads is strongly affected by the soil structure (pile) interaction. The forces exerted by waves are most dominant among the lateral environmental forces which governing the jacket structures design especially the foundation piles. The present investigation is to perform a static wave analysis on a typical fixed offshore platform for extreme environmental conditions, and to study the effects of the combined lateral and vertical loads on pile group foundation. The three dimensional modeling and analysis of the offshore platform are done using finite difference method. The present analysis was done under static condition considering the structural and the environmental loads at extreme environmental conditions, by reaching the state of static equilibrium. A parametric study has been done by varying the seabed slope to examine the variation in soilstructure interaction behaviour of piles. It has been found that the lateral displacement at the pile top and at the seabed level increases as the seabed slope increases. It is also noticed that the depth at which the maximum shear force and bending moment occurs from the pile top increases as the slope of the seabed increases.

1 Introduction

Piles are also subjected to significant amount of lateral loads and overturning moments besides axial load. Lateral loads are in the order of 10–15 % of the vertical loads in the case of onshore structures, and in the case of coastal and offshore structures these lateral loads can exceed 30 % of the vertical loads (Narasimha Rao et al. 1998). Hence, the foundation piles have a significant effect on the response of fixed offshore structures due to lateral loading. Among all the environmental forces, wave forces and forces due to ocean currents associated with the waves contribute the most to the total lateral forces experienced by the offshore structures. Therefore, proper attention has to be given in designing such pile structures of fixed offshore platforms under lateral loads. Piles are commonly selected as a cost effective option for the support of raised structures, highway infrastructures, and offshore platforms. These structural members are often subjected to considerable lateral forces such as wind loads in hurricane prone areas, earthquake loads in areas of seismic activity, and wave loads in offshore environments. Soilstructure interaction is the mechanism that governs the pile response behaviour and the ultimate capacity of the structure for the applied loads. A common approach to the analysis of laterally loaded piles is the load-transfer approach, which involves treating the soil as a series of springs down the length of the pile. Upon defining the deformational characteristics of the soil medium, the flexural behaviour of the foundation and the condition at the interface, the soil-foundation interaction problem is basically reduced to the determination of the contact stress distribution at the interface. Once the contact stresses are determined, it is possible to evaluate the deflections, flexural moments and shear forces in the foundation and the corresponding stresses and displacements in the soil medium.